API update for fuse_loop_config additions

struct fuse_loop_config was passed as a plain struct, without any
version identifer. This had two implications

1) Any addition of new parameters required a FUSE_SYMVER for
fuse_session_loop_mt() and fuse_loop_mt() as otherwise a read
beyond end-of previous struct size might have happened.

2) Filesystems also might have been recompiled and the developer
might not have noticed the struct extensions and unexpected for
the developer (or people recomliling the code) uninitialized
parameters would have been passed.


Code is updated to have struct fuse_loop_config as an opaque/private
data type for file systems that want version 312
(FUSE_MAKE_VERSION(3, 12)). The deprecated fuse_loop_config_v1
is visible, but should not be used outside of internal
conversion functions

File systems that want version >= 32 < 312 get the previous
struct (through ifdefs) and the #define of fuse_loop_mt
and fuse_session_loop_mt ensures that these recompiled file
systems call into the previous API, which then converts
the struct. This is similar to existing compiled applications
when just libfuse updated, but binaries it is solved with
the FUSE_SYMVER ABI compact declarations.

Signed-off-by: Bernd Schubert <bschubert@ddn.com>

3 files changed, 69 insertions, 20 deletions

diff --git a/include/fuse.h b/include/fuse.h
index 1a2f841..917a91c 100644
--- a/include/fuse.h
+++ b/include/fuse.h
@@ -1011,6 +1011,9 @@ void fuse_exit(struct fuse *f);
 #if FUSE_USE_VERSION < 32
 int fuse_loop_mt_31(struct fuse *f, int clone_fd);
 #define fuse_loop_mt(f, clone_fd) fuse_loop_mt_31(f, clone_fd)
+#elif FUSE_USE_VERSION < FUSE_MAKE_VERSION(3, 12)
+int fuse_loop_mt_32(struct fuse *f, struct fuse_loop_config *config);
+#define fuse_loop_mt(f, config) fuse_loop_mt_32(f, config)
 #else
 /**
  * FUSE event loop with multiple threads
diff --git a/include/fuse_common.h b/include/fuse_common.h
index 3f7260c..b40814f 100644
--- a/include/fuse_common.h
+++ b/include/fuse_common.h
@@ -23,7 +23,7 @@
 #define FUSE_MAJOR_VERSION 3
 
 /** Minor version of FUSE library interface */
-#define FUSE_MINOR_VERSION 11
+#define FUSE_MINOR_VERSION 12
 
 #define FUSE_MAKE_VERSION(maj, min)  ((maj) * 100 + (min))
 #define FUSE_VERSION FUSE_MAKE_VERSION(FUSE_MAJOR_VERSION, FUSE_MINOR_VERSION)
@@ -104,11 +104,20 @@ struct fuse_file_info {
 	uint32_t poll_events;
 };
 
+
+
 /**
  * Configuration parameters passed to fuse_session_loop_mt() and
  * fuse_loop_mt().
+ * Deprecated and replaced by a newer private struct in FUSE API
+ * version 312 (FUSE_MAKE_VERSION(3, 12)
  */
+#if FUSE_USE_VERSION < FUSE_MAKE_VERSION(3, 12)
+struct fuse_loop_config_v1; /* forward declarition */
 struct fuse_loop_config {
+#else
+struct fuse_loop_config_v1 {
+#endif
 	/**
 	 * whether to use separate device fds for each thread
 	 * (may increase performance)
@@ -128,6 +137,7 @@ struct fuse_loop_config {
 	unsigned int max_idle_threads;
 };
 
+
 /**************************************************************************
  * Capability bits for 'fuse_conn_info.capable' and 'fuse_conn_info.want' *
  **************************************************************************/
@@ -834,6 +844,39 @@ int fuse_set_signal_handlers(struct fuse_session *se);
  */
 void fuse_remove_signal_handlers(struct fuse_session *se);
 
+/**
+ * Create and set default config for fuse_session_loop_mt and fuse_loop_mt.
+ *
+ * @return anonymous config struct
+ */
+struct fuse_loop_config *fuse_loop_cfg_create(void);
+
+/**
+ * Free the config data structure
+ */
+void fuse_loop_cfg_destroy(struct fuse_loop_config *config);
+
+/**
+ * fuse_loop_config2 setter to set the number of max idle threads.
+ */
+void fuse_loop_cfg_set_idle_threads(struct fuse_loop_config *config,
+				    unsigned int value);
+
+/**
+ * fuse_loop_config2 setter to enable the clone_fd feature
+ */
+void fuse_loop_cfg_set_clone_fd(struct fuse_loop_config *config,
+				unsigned int value);
+
+/**
+ * Convert old config to more recernt fuse_loop_config2
+ *
+ * @param config current config2 type
+ * @param v1_conf older config1 type (below FUSE API 312)
+ */
+void fuse_loop_cfg_convert(struct fuse_loop_config *config,
+			   struct fuse_loop_config_v1 *v1_conf);
+
 /* ----------------------------------------------------------- *
  * Compatibility stuff					       *
  * ----------------------------------------------------------- */
diff --git a/include/fuse_lowlevel.h b/include/fuse_lowlevel.h
index d73e9fa..378742d 100644
--- a/include/fuse_lowlevel.h
+++ b/include/fuse_lowlevel.h
@@ -1968,26 +1968,29 @@ int fuse_session_mount(struct fuse_session *se, const char *mountpoint);
 int fuse_session_loop(struct fuse_session *se);
 
 #if FUSE_USE_VERSION < 32
-int fuse_session_loop_mt_31(struct fuse_session *se, int clone_fd);
-#define fuse_session_loop_mt(se, clone_fd) fuse_session_loop_mt_31(se, clone_fd)
+	int fuse_session_loop_mt_31(struct fuse_session *se, int clone_fd);
+	#define fuse_session_loop_mt(se, clone_fd) fuse_session_loop_mt_31(se, clone_fd)
+#elif FUSE_USE_VERSION < FUSE_MAKE_VERSION(3, 12)
+	int fuse_session_loop_mt_32(struct fuse_session *se, struct fuse_loop_config *config);
+	#define fuse_session_loop_mt(se, config) fuse_session_loop_mt_32(se, config)
 #else
-#if (!defined(__UCLIBC__) && !defined(__APPLE__))
-/**
- * Enter a multi-threaded event loop.
- *
- * For a description of the return value and the conditions when the
- * event loop exits, refer to the documentation of
- * fuse_session_loop().
- *
- * @param se the session
- * @param config session loop configuration 
- * @return see fuse_session_loop()
- */
-int fuse_session_loop_mt(struct fuse_session *se, struct fuse_loop_config *config);
-#else
-int fuse_session_loop_mt_32(struct fuse_session *se, struct fuse_loop_config *config);
-#define fuse_session_loop_mt(se, config) fuse_session_loop_mt_32(se, config)
-#endif
+	#if (!defined(__UCLIBC__) && !defined(__APPLE__))
+		/**
+		 * Enter a multi-threaded event loop.
+		 *
+		 * For a description of the return value and the conditions when the
+		 * event loop exits, refer to the documentation of
+		 * fuse_session_loop().
+		 *
+		 * @param se the session
+		 * @param config session loop configuration
+		 * @return see fuse_session_loop()
+		 */
+		int fuse_session_loop_mt(struct fuse_session *se, struct fuse_loop_config *config);
+	#else
+		int fuse_session_loop_mt_312(struct fuse_session *se, struct fuse_loop_config *config);
+		#define fuse_session_loop_mt(se, config) fuse_session_loop_mt_312(se, config)
+	#endif
 #endif
 
 /**